1. Field of the Invention
This invention relates to an exposure device and exposure method, and in particular to an exposure device and exposure method which are suitable for use in holographic exposure technology. It also relates to a method of manufacture of semiconductor devices, of which transistors and integrated circuits are representative. It also relates to electro-optical devices and electronic appliance which uses active elements to drive an electro-optical layer such as liquid crystals, electroluminescence devices, or a disperse medium in which are dispersed electrophoretic particles.
2. Description of the Related Art
A fine pattern exposure technique utilizing so-called hologram exposure devices is attracting attention for use in semiconductor device patterning processes. In this exposure technique, first a pattern drawn on a photomask (original reticle) is caused to be recorded at the same size on the hologram recording face of an exposure plate, to create a hologram mask; then, by irradiating this hologram mask with reproduction light, the pattern information recorded on the hologram mask is reproduced on a film of resist or other photosensitive material, followed by exposure of a fine processing pattern.
A holographic exposure method employing this exposure principle in principle involves no aberrations due to lenses, since optical lenses are not required for radiation of exposure light; hence higher resolutions are obtained than in lithographic exposure methods. Further, there is compatibility with i-line processes which target high-resolution exposure. Also, there is the advantage that the equipment construction is relatively simple, and as a result the cost of equipment construction can be kept low.
In the holographic exposure method of the prior art, the exposure dose and focus are adjusted at the beginning of exposure, and the pattern exposure is repeated for these exposure conditions, to perform exposure of the entire substrate surface.
However, the holographic exposure method of the prior art has a number of problems.
First, while the resolution of the holographic exposure technique is high compared with that of ordinary mask exposure methods, in principle the focal depth is shallow. Hence the range in the depth direction of the photosensitive material film over which patterning is possible in a single exposure is narrow compared with ordinary mask exposure; for example, in a case in which exposure is to be performed so as to obtain a desired exposure pattern in a photosensitive material film formed on a substrate which has already been patterned, and the surface of which has depressions and protrusions, often it is necessary to perform so-called multiple exposure, in which the exposure is performed in several passes.
When the substrate for exposure is made larger in area, as for example when exposure a wafer 6 to 7 inches in diameter, the substrate itself may have warping or undulations. Even if a photosensitive material is formed to a uniform film thickness on a substrate with such poor flatness, because the flatness may be as large as 10 μm or more for every 10 cm, if exposure is performed using a holographic exposure device having a shallow focal depth in principle, the patterning dimensions after exposure will deviate greatly from the design values. In particular, when photosensitive material is applied to a substrate the surface of which has poor flatness, such as a glass substrate, the error in the patterning dimensions may be even greater.